The present invention is generally directed to an electrical sensing tool More particularly, the present invention is directed to a voltage sensing hand tool which includes a non-contact voltage sensing circuit and an associated alarm circuit.
Electricians, technicians, maintenance people and others who work with and around electrical distribution and wiring systems often work in the vicinity of energized electrical panels and wires. Good practice dictates that these electrical circuits be de-energized when work is performed. Not infrequently, however, through error or oversight, these circuits remain in an energized condition during maintenance, thereby presenting an electrical hazard to both the worker and to the associated electrical equipment.
One particular hazard is encountered when conductive hand tools such as wire strippers, cutters, pliers, screwdrivers and such are employed in maintenance procedures. When these hand tools come into contact with the live electrical circuits, they can cause both injury to the worker and damage to the electrical equipment.
Due to these problems, hand held tools that include a voltage meter embedded in the handle have been developed. The voltage meter provides an indication to the user that a voltage is present on the wire and that, therefore, a live wire has been contacted. Such devices, however, require actual, physical contact with the live wire or circuit before the user is alerted. These are useful when the user is probing for a live wire. These devices do not provide a sufficient warning to an unsuspecting user contacting a high voltage circuit to prevent injury or damage. Furthermore, these devices do not provide any indication of contact with a live wire when the wire is insulated.
Also available in the art are non-contact voltage indicators, also useful to probe for a live wire. These indicators provide a visual or audio indicator to the user when the indicator is placed in the vicinity of an AC voltage. An example of a device of this type is shown, for example, in U.S. Pat. No. 5,877,618 xe2x80x9cHand Held Non-Contact Voltage Testerxe2x80x9d. While useful in providing an indication of a live wire, successful use of this device requires the user to test the wire before work is begun. The test, therefore, does not solve the initial problem: erroneously or mistakenly forgetting to disable or verify disablement of the circuit before work is begun.
Neither of these prior art devices therefore can actively alert the user of the possibility of hazardous voltages on the wires, cables or other electrical devices prior to potentially dangerous contact.
Thus there remains a need for a hand tool that intrinsically alerts a user when the tool is placed in the vicinity of a wire or cable that has a hazardous voltage impressed on it.
The present invention is a low cost, reliable and easy-to-use hand tool providing an alert signal to a user prior to contacting a live wire. The device of the present invention integrates a non-contact voltage alert circuit and associated alarm circuitry into a hand tool, thereby providing a high degree of safety for the user. The alarm circuitry provides a visual or audio signal, alerting the user that contact with a live wire is about to be made.
An object of the invention is to provide a low cost method for alerting the user of a hand tool, such as a wire stripper, that an AC voltage is impressed on the wire or cable being examined.
A further object of the invention is to provide a visual or audible alert to the user when an AC voltage is detected.
A further object of the invention is to provide a non-contact means for determining the presence of an AC voltage.
Other features of the invention and advantages will become apparent upon reading the material provided hereafter.